Inorg. Chem. 2005, 44, 1740−1751
Mono-, Di-, and Tricoordinated Phosphorus Attached to a N−N Unit: An Experimental and Theoretical Study† Gerd Fischer, Sebastian Herler, Peter Mayer,‡ Axel Schulz,* Alexander Villinger, and Jan J. Weigand Department of Chemistry and Biochemistry, Ludwig-Maximilians-UniVersita¨t Mu¨nchen Butenandtstrasse 5-13 (Haus F), 81377 Mu¨nchen, Germany Received December 7, 2004
N,N′,N′-[Tris(trimethylsilyl)]hydrazino-diphenylphosphane, (TMS)2N−(TMS)N−PPh2 (1), and N,N′,N′-[tris(trimethylsilyl)]hydrazino-phenyl(chloro)phosphane, (TMS)2N−(TMS)N−P(Cl)Ph2 (2), were obtained in the reaction of bis-[lithiumtris(trimethylsilyl)hydrazide] with PhnPCl3 - n (n ) 1, 2). The structure and bonding of both species are discussed on the basis of experimentally observed (X-ray, Raman, NMR, and MS) and theoretically obtained data (B3LYP/ 6-31G(d,p), NBO analysis). Oxidation with sulfur and selenium results in the formation of (TMS)2N−(TMS)N−P(S)Ph2 (4), (TMS)2N−(TMS)N−P(Se)Ph2 (5), (TMS)2N−(TMS)N−P(S)Ph(Cl) (6), and (TMS)2N−(TMS)N−P(Se)Ph(Cl) (7). Moreover, the thermal decomposition of N,N′,N′-[tris(trimethylsilyl)]hydrazine-dichlorophosphane, (TMS)2N− (TMS)N−PCl2 (3) and the reaction with magnesium have been investigated. The formation and molecular structure of the novel MgCl2(THF)2‚2Mg[(TMS)NP(O)2N(TMS)2](THF) (8) salt containing the hitherto unknown (TMS)NP(O)2N(TMS)22− anion are discussed. DFT calculations (B3LYP/6-311+G(3df,2p)//B3LYP/6-31G(d,p)) are used to evaluate the bonding, ground-state structures, and energy landscape for the different isomers of 3: the thermodynamics and kinetics of the successive elimination of chlorotrimethylsilane (TMS−Cl) resulting in the formation of covalent azide analogues such as TMS−PNN or TMS−NNP.
Introduction The low-coordination-number chemistry of the group 15 elements (N, P) has been developed extensively in the past thanks to the use of bulky groups.1 It has been possible to characterize these reactive species because of their kinetic and thermodynamic stabilization by appropriate substitution. It was not until 1973 that Flick and Niecke were able to prove the existence of a phosphorus(III) compound with the structural feature of a phosphazene, -PdN-.2 This first iminophosphane, a phosphazene with phosphorus in coordination number 2, was obtained in the reaction of bis(trimethylsilyl)amino(difluoro)phosphane with lithium-bis(trimethylsilyl)amide (eq 1) (Me3Si)2N-PF2 + LiN(SiMe3)2 f (Me3Si)2N-PdSiMe3 + LiF + Me3Si-F (1) * To whom correspondence should be addressed. E-mail: lex@ cup.uni.muenchen.de. Fax: +49-89-218077492. Phone: +49-89-218077772. † Dedicated to my father Dr. W. Schulz on the occasion of his 70th birthday. ‡ Performed X-ray structure analysis. (1) (a) Multiple Bonds and Low Coordination in Phosphorus Chemistry; Regitz, M., Scherer, O. J., Eds.; G. Thieme Verlag: Stuttgart, Germany, 1990. (b) Weber, L. Chem. ReV. 1992, 92, 1839. (c) Weber, L. Chem. Ber. 1996, 129, 367.
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Shortly thereafter, phosphorus-nitrogen compounds with a two-coordinated phosphorus(III) atom represented a wellestablished group.3-5 Because of the large number of stable low-coordinated phosphorus-nitrogen compounds, these species can no longer be regarded as exotic among the main group element compounds. This class of P-N compounds (2) Niecke, E.; Flick, W. Angew. Chem. 1973, 85, 586-587. Niecke, E.; Flick, W. Angew. Chem., Int. Ed. Engl. 1973, 12, 585-586. (3) (a) Scherer, O. J.; Kuhn, N. Angew. Chem. 1974, 86, 899. Scherer, O. J.; Kuhn, N. Angew. Chem., Int. Ed. Engl. 1974, 13, 811. (b) Niecke, E.; Scherer O. J. Nachr. Chem. Tech. 1975, 23, 395. (c) Scherer, O. J.; Kuhn, N. J. Organomet. Chem. 1974, 82, C3. (d) Scherer, O. J.; Kuhn, N. Chem. Ber. 1974, 107, 2123-2125. (e) Fleming, S.; Lupton, M. K.; Jekot, K. Inorg. Chem. 1972, 11, 2534. (f) Maryanoff, B. E.; Hutchins, R. O. J. Org. Chem. 1972, 37, 3475. (g) Thomas, M. G.; Kopp, R. W.; Schultz, C. W.; Parry, R. W. J. Am. Chem. Soc. 1974, 96, 2646. (h) No¨th, H.; Ullmann, R. Chem. Ber. 1976, 109, 1942. (i) Scherer, O. J.; Schnabl, G. Chem. Ber. 1976, 109, 2996. (j) Niecke, E.; Kro¨her, R. Angew. Chem. 1976, 88, 758. Niecke, E.; Kro¨her, R. Angew. Chem., Int. Ed. Engl. 1976, 15, 692. (k) Thomas, M. G.; Schultz, C. W.; Parry, R. W. Inorg. Chem. 1977, 16, 994. (l) Charbonnel, Y.; Barrans, J. Tetrahedron 1976, 32, 2039. (m) Schmidpeter, A.; Luber, J.; Tautz, H. Angew. Chem. 1977, 89, 554. Schmidpeter, A.; Luber, J.; Tautz, H. Angew. Chem., Int. Ed. Engl. 1977, 16, 546. (4) (a) Pohl, S. Chem. Ber. 1979, 112, 3159-3165. (b) Pohl, S. Angew. Chem. 1976, 21, 723. Pohl, S. Angew. Chem., Int. Ed. Engl. 1976, 11, 687-688. (5) Niecke, E.; Gudat, D. Angew. Chem. 1991, 103, 251-270. Niecke, E.; Gudat, D. Angew. Chem., Int. Ed. Engl. 1991, 30, 0, 217-237 and references therein.
10.1021/ic048286m CCC: $30.25
© 2005 American Chemical Society Published on Web 02/10/2005
Phosphorus Attached to a N-N Unit Scheme 1
is characterized by large structural diversity and unusual chemical behavior, mainly originating in the (3p-2p)πP-N bond system representing a highly electronegative fragment including a lone pair. The synthesis of PN species containing a two-coordinated phosphorus(III) atom such as the iminophosphanes, R2NPdNR, can be achieved by (i) 1.2 elimination,5 (ii) substitution reaction starting from a known iminophosphane,6 (iii) conversions5 for example, by a 1.3 shift of a silyl group,7 and (iv) ring opening, for example, by thermal treatment of λ3, λ5 aza-diphosphiridines.8 The most convenient synthesis method seems to be the 1.2 elimination of Me3Si-X from aminophosphanes, which can be generated easily by reaction of PX3 with lithium amides (eq 2, R ) TMS, X ) F, Cl, and Br).3a,5 -LiX
-LiX
PX3 + LiNR2 98 X2P-NR2 + LiNR2 98 ∆, -RX
XP(NR2)2 98 R2N-PdN-R (2) Much less is known about compounds containing the NNP moiety. With respect to the coordination number at the phosphorus(III) atom, these species can be divided into five classes with a neutral NNP moiety as displayed in Scheme 1. A (aminophosphane) and C represent tricoordinated phosphorus species or can be regarded as either hydrazine or diazene derivatives. B is a phosphinidenehydrazine9 and represents, in addition to D, a dicoordinated phosphorus species. Furthermore, D and E can be viewed as N- or P-substituted analogues of covalently bound azides. Monocoordinated phosphorus species E with a formal NP triple bond can also be considered to be a phosphinidyne derivative. (6) (a) Scherer, O. J.; Kulbach, N.-T.; Gla¨ssel, W. Z. Naturforsch., B: Anorg. Chem., Org. Chem. 1978, 33, 652. (b) Niecke, E.; Nieger, M.; Reichert, F. Angew. Chem. 1988, 100, 1781. Niecke, E.; Nieger, M.; Reichert, F. Angew. Chem., Int. Ed. Engl. 1988, 27, 1715. (c) Romanenko, V. D.; Ruban, A. V.; Markovskii, L. N. Zh. Obshch. Khim. 1983, 53, 778. (d) Romanenko, V. D.; Ruban, A. V.; Chernega, A. N.; Markovskii, L. N. Zh. Obshch. Khim. 1988, 58, 2802. (e) Romanenko, V. D.; Ruban, A. V.; Chernega, A. N.; Povolotskii, M. I.; Antipin, Y. M.; Struchkow, Y. T.; Markovskii, L. N. Zh. Obshch. Khim. 1988, 58, 948. (f) Niecke, E.; Nieger, M.; Ga¨rtner-Winkhaus, C.; Kramer, B. Chem. Ber. 1990, 123, 477. (g) Niecke, E.; Altmeyer, O.; Barion, D.; Detsch, R.; Ga¨rtner-Winkhaus, C.; Hein, M.; Nieger, M.; Reichert, F. Phosphorus, Sulfur Silicon Relat. Elem. 1990, 49/50, 321. (h) Niecke, E.; Detsch, R.; Nieger, M. Chem. Ber. 1990, 123, 797. (7) Zurmu¨hlen, F.; Regitz, M. Angew. Chem. 1987, 99, 65. Zurmu¨hlen, F.; Regitz, M. Angew. Chem., Int. Ed. Engl. 1987, 26, 83. (8) (a) Niecke, E.; Lysek, M.; Symalla, M. Chimia 1986, 40, 202. (b) Niecke, E.; Ru¨ger, R.; Schoeller, W. W. Angew. Chem. 1981, 93, 1110. Niecke, E.; Ru¨ger, R.; Schoeller, W. W. Angew. Chem., Int. Ed. Engl. 1981, 20, 1034. (9) David, G.; von der Gonna, V.; Niecke, E.; Busch, T.; Schoeller, W. W.; Rademacher, P. J. Chem. Soc., Faraday Trans. 1994, 90, 26112616.
Hydrazine derivatives of type A have been synthesized by Klingebiel et al. in the reaction of bis[lithium-tris(trimethylsilyl)-hydrazide] with PF3.10 When (TMS)2N(TMS)N-PF2 was reacted with LiN(SiMe3)(CMe3), an unsaturated species of type B could be observed. The authors concluded that salt elimination of LiF is followed by the elimination of Me3SiF, yielding (TMS)2N-NdP-N(TMS)(CMe3). The first structural characterization of a type B species was published by Niecke et al. and displayed a rather long P-N bond of 1.598 Å in (tetramethylpiperidino)bis(trimethylsilyl)diazaphosphene. This amino(diaza)phosphene was prepared by treating N-(dichlorophosphino)-(2,2,6,6tetramethyl)piperidine with LiN(SiMe3)2.11 To the best of our knowledge, compounds analogous to covalent azides such as species D and E (Scheme 1) are not known as well as the all triatomic binary anions composed exclusively of phosphorus and nitrogen atoms and the phosphorus analogue of the azide anion: NdNdP-, NdPdN-, PdNdP-, PdPdN-, PdPdP-. The potential energy surfaces of these anions have been calculated using ab initio methods. According to these theoretical results, the N3- and N2P- ions have linear structures; P3- and P2Npossess several isomers (linear, bent, or cyclic) close to each other on the energetic scale.12 The nature of PN single and double bonds has been extensively studied;5,13 P-P and PdP bonds are somewhat more elusive.14 There are only a few examples of compounds containing the NdP-P unit, which is isomeric with P-N-P species. Recently, Dyson et al. showed the reversible rearrangement that is triggered by protonation/deprotonation between diphosphinamines (P-N-P) and iminobiphosphines (NdP-P).14a As part of our research directed toward the synthesis of R-PNN or PNN-R species, we are interested in reactions of the following type -LiCl
(i) RnPCl3 - n + 1/2[LiN(TMS)N(TMS)2]2 98 (TMS)2N-(TMS)N-P(Cl2 - n)Rn (3) with R ) Ph and n ) 0, 1, 2; (ii) reduction of the (TMS)2N(TMS)N-P(Cl2 - n)Rn (n ) 0, 1) with magnesium; and (iii) quenching NNP intermediates by the oxidation reaction with oxygen, sulfur, or selenium. In these experiments, we have observed the formation of new compounds such as (TMS)2N(10) Bode, K.; Klingebiel, U., Noltemeyer, M.; Witte-Abel, H. Z. Anorg. Allg. Chem. 1995, 621, 500-505. (11) Dressler, U.; Niecke, E.; Pohl, S.; Saak, W.; Schoeller, W. W.; Schaefer, H. G. J. Chem. Soc., Chem. Commun. 1986, 14, 10861087. (12) Chaban, G. M.; Klimenko, N. M.; Charkin, O. P. Ser. Khim. 1990, 7, 1590-1597. (b) Charkin, O. P.; McKee, M. L.; Schleyer, P. v. R. Z. Neorgan. Khim. 1998, 43, 280-293. (13) (a) Burford, N.; Cameron, T. S.; Conroy, K. D.; Ellis, B.; Lumsden, M.; Macdonald, C. L. B.; McDonald, R.; Phillips, A. D.; Ragogna, P. J.; Schurko, R. W.; Walsh, D.; Wasylishen, R. E. J. Am. Chem. Soc. 2002, 124, 14012. (b) Burford, N.; Cameron, T. S.; LeBlanc, D. J.; Phillips, A. D.; Concolino, T. E.; Lam, K.-C.; Rheingold, A. L. J. Am. Chem. Soc. 2000, 122, 5413. (c) Burford, N.; Ragogna, P. J.; McDonald, R.; Ferguson, M. J. Chem. Commun. 2003, 2066. (d) Merceron, N.; Miqueu, K.; Baceiredo, A.; Bertrand, G. J. Am. Chem. Soc. 2002, 124, 6806.
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Fischer et al. (TMS)N-P(Cl2 - n)Rn (m ) 1, 2) together with the previously described species (TMS)NPN(TMS)22,3a under modified reaction conditions. Bis[lithium-tris(trimethylsilyl)-hydrazide] seems to be a good precursor to introduce the NNP moiety via salt elimination, resulting in the formation of tetrasubstituted hydrazines.10,15 The reaction of PCl3 with [LiN(TMS)N(TMS)2]2 has already been described by Niecke et al., yielding (TMS)2N-(TMS)N-PCl2 (3).16 In this paper, we report (i) our experimental results of the above-mentioned reactions of bis[lithium-tris(trimethylsilyl)hydrazide]10,15 with RnPCl3 - n and (ii) our theoretical study of the potential energy surface of (TMS)2N-(TMS)N-PCl2 with respect to the loss of chlorosilane, resulting in the formation of TMS-NNP, (TMS)2N-NdP-Cl, and (TMS)2NPN(TMS) species. Experimental Section General Remarks. Solvents were freshly distilled, dried, and stored under nitrogen. NMR: JEOL Eclipse 400 and 270 (1H, 13C chemical shifts refer to δTMS ) 0.00; 31P refers to δH3PO4(85%) ) 0.00). IR: Nicolet 520 FT-IR (as KBr pellets or in Nujol mulls between KBr windows). Raman: Perkin-Elmer spectrum 2000R NIR FT equipped with a Nd:YAG laser (1064 nm). CHN analyses: Analysator Elementar Vario EL. MS: JEOL MStation JMS 700. Melting points are uncorrected (Bu¨chi B540). Bis[lithiumtris(trimethylsilyl)-hydrazide] was prepared according to the procedure given in the literature.10,15 Synthesis of N,N′,N′-[Tris(trimethylsilyl)]hydrazino-(diphenyl)phosphane, (TMS)2N-(TMS)N-PPh2 (1). Into a solution of 1 g (1.95 mmol) of bis[lithium-tris(trimethylsilyl)-hydrazide] in hexane (75 mL), a solution of 0.867 g (3.9 mmol) of freshly distilled ClPPh2 in hexane (25 mL) was added during a period of 1 h at ambient temperature. The white precipitate that was formed (LiCl) was separated by filtration after 2 h. The hexane was removed in vacuum, and a white waxy solid (1) was obtained, which still contained traces of LiCl. 1 was purified by sublimation (110 °C, 10-3 mbar). (TMS)2N-(TMS)N-PPh2 (432.76) yield: 1.65 g (98%) colorless crystals, mp 108 °C. IR (KBr, cm-1): ν˜ 3075 w, 3047 w, 2974 m, 2952 m, 2896 m, 1585 w, 1520 w, 1436 m, 1430 m, 1404 w, 1310 w, 1264 s, 1248 vs, 1242 s, 1179 m, 1104 m, 1085 w, 1067 w, 1030 m, 1014 s, 910 vs, 879 vs, 854 vs, 835 vs, 817 vs, 774 s, 740 s, 705 m, 695 s, 672 s, 618 m, 607 m, 512 m, 487 m, 465 m, 419 w, 385 s, 372 m. Raman (200mW, 25 °C, cm-1): ν˜ 3172 (0.5), 3138 (0.5), 3055 (9), 2977 (5), 2954 (6), 2899 (10), 1588 (9), 1573 (3), 1410 (2, br), 1180 (2), 1157 (2), 1103 (3), 1089 (3), 1030 (4), 1002 (10), 678 (3), 643 (5), 619 (3), 467 (2), 420 (14) (a) Fei, Z.; Biricik, N.; Zhao, D.; Scopelliti, R.; Dyson, P. J. Inorg. Chem. 2004, 43, 2228-2230. (b)Yoshifuji, M.; Shima, I.; Inamoto, N.; Hirotsu, K.; Higuchi, T. J. Am. Chem. Soc. 1981, 103, 4587. (c) Yoshifuji, M.; Shibayama, K.; Inamoto, N.; Matsushita, T.; Nishimoto, K. J. Am. Chem. Soc. 1983, 105, 2495. (d) Kaukorat, T.; Neda, I.; Schmutzler, R. Coord. Chem. ReV. 1994, 137, 53. (e) Burford, N.; Cameron, T. S.; LeBlanc, D. J.; Losier, P.; Sereda, S.; Wu, G. Organometallics 1997, 16, 4712. (f) Kato, T.; Gornitzka, H.; Baceiredo, A.; Schoeller, W. W.; Bertrand, G. Science 2000, 289, 754. (g) Kato, T.; Gornitzka, H.; Baceiredo, A.; Schoeller, W. W.; Bertrand, G. J. Am. Chem. Soc. 2002, 124, 2506. (15) (a) K. Seppelt, W. Sundermeyer, Chem. Ber. 1969, 102, 1247-1252. (b) Metzler, N.; No¨th, H.; Sachdev, H. Angew. Chem. 1994, 106, 1837-1839. Metzler, N.; No¨th, H.; Sachdev, H. Angew. Chem., Int. Ed. Engl. 1994, 17, 1746-1748. (16) Niecke, E.; Altmeyer, O.; Nieger, M.; Knoll, F. Angew. Chem. 1987, 99, 1299-1300. Niecke, E.; Altmeyer, O.; Nieger, M.; Knoll, F. Angew. Chem., Int. Ed. Engl. 1987, 26, 1257.
1742 Inorganic Chemistry, Vol. 44, No. 6, 2005
1H
NMR (CDCl3, (3), 404 (3), 388 (1), 332 (1), 261 (4), 210 (4). 25 °C): δ 0.08 (s, 18 H, TMS), 0.10 (s, 9 H, TMS), 7.32 (m, 4 H, Ph), 7.61 (m, 6 H, Ph). 13C NMR (CDCl3, 25 °C): δ 4.04 (s, N(Si(CH3)3)2), 4.07 (s, NSi(CH3)3), 127.94 (d, 3JCP ) 6.2 Hz, Cphenyl), 128.99 (s, br Cphenyl), 134.5 (d, 2JCP ) 22.8 Hz, Cphenyl), 140.08 (d, 1J 31P NMR (CDCl , 25 °C): δ 61.4 (s). CP ) 20.8 Hz, Cphenyl). 3 29Si{1H} NMR (CDCl , 270 MHz, 25 °C): δ 8.93 (d, 3J 3 SiP ) 1.3 Hz, N(Si(CH3)3)2), 13.42 (d, 2JSiP ) 7.9 Hz, NSi(CH3)3). MS (EI, 70 eV, >5%) m/z (%): 432 (3) [M+], 417 (10) [M+ - CH3], 332 (6), 331 (20), 321 (8) [(TMS)2NN(TMS)2+], 320 (23) [((TMS)2NN(TMS)2 - H)+], 305 (7) [((TMS)2NN(TMS)2 - CH3)+], 273 (8) [(TMS)HN-PPh2+], 272 (30) [(TMS)N-PPh2+], 248 (5) [(TMS)2N-NH(TMS)+], 247 (14) [(TMS)2N-N(TMS)+], 232 (7), 231 (15), 218 (8), 217 (28), 204 (9), 197 (7), 175 (6), 174 (30), 146 (12) [TMS-TMS+], 135 (15), 131 (7), 130 (22), 74 (9) [HSi(CH3)3+], 73 (100) [SiCH3)3+], 45 (5). C21H37N2P1Si3 (432.76): calcd C 58.28, H 8.62, N 6.47; found C 58.63, H 8.44, N 6.02. HR-MS: C21H37N2P1Si3 (432.76) requires M+ ) 432.2002; found 432.2002. Synthesis of N,N′,N′-[Tris(trimethylsilyl)]hydrazino-phenyl(chloro)phosphane, (TMS)2N-(TMS)N-P(Cl)Ph (2). Into a solution of 1 g (1.95 mmol) of bis[lithium-tris(trimethylsilyl)hydrazide] in hexane (75 mL), a solution of 0.703 g (3.9 mmol) of freshly distilled Cl2PPh in hexane (25 mL) was added during a period of 1 h at ambient temperature. The white precipitate that was formed (LiCl) was separated by filtration after 2 h. The hexane was removed in vacuum, and a waxy solid (2) was obtained, which still contained traces of LiCl. 2 was purified by sublimation (110 °C, 10-3 mbar). (TMS)2N-(TMS)N-P(Cl)Ph (391.11) yield: 1.45 g (95%) colorless crystals, mp 118 °C. IR (KBr, cm-1): ν˜ 3059 m, 3057 m, 2955 s, 2900 m, 1586 w, 1479 m, 1434 s, 1405 m, 1307 w, 1251 vs, 1249 vs, 1182 w, 1156 w, 1089 s, 1013 s, 913 br vs, 881 vs, 836 vs, 769 s, 742 vs, 699 vs, 661 s, 619 m, 607 m, 581 m, 500 br m, 465 m, 438 w, 417 w, 387 m. Raman (300 mW, 25 °C, cm-1): ν˜ 3172 (0.5), 3144 (0.5), 3067 (7), 3048 (3), 2956 (5), 2903 (10), 1587 (4), 1574 (1), 1411 (2), 1183 (1), 1159 (1), 1089 (1), 1029 (3), 1003 (5), 689 (2), 666 (2), 648 (6), 620 (1), 499 (1), 448 (3), 413 (1), 372 (4), 346 (1), 272 (5), 197 (3, br). 1H NMR (CDCl3, 25 °C): δ 0.01 (s, 9 H, TMS), 0.27 (s, 18 H, TMS), 7.42 (m, 2 H, Ph), 7.95 (m, 3 H, Ph). 13C NMR (CDCl3, 25 °C): δ 3.05 (s, NSi(CH3)3)2), 3.09 (s, NSi(CH3)3), 128.1 (d, 3JCP ) 6.1 Hz, Cphenyl), 130.6 (s, Cphenyl), 132.6 (d, 2JCP ) 26.1 Hz, Cphenyl), 138.20 (d, 1JCP ) 38.4 Hz, Cphenyl). 31P NMR (CDCl3, 25 °C): δ 145.2 (s). 29Si{1H} NMR (CDCl3, 25 °C): δ 11.3 (s, N(Si(CH3)3)2), 19.1 (d, 2JSiP ) 2.0 Hz, NSi(CH3)3). MS (EI, 70 eV, >5%) m/z (%): 390 (3) [M+], 375 (6) [M+ - CH3], 289 (5), 248 (8) [(TMS)2N-NH(TMS)+], 247 (32) [(TMS)2N-N(TMS)+], 174 (25), 146 (12) [TMS-TMS+], 135 (9), 131 (7), 130 (12), 74 (9) [HSi(CH3)3+], 73 (100) [SiCH3)3+], 45 (6), 36 (7). C15H32Cl1N2P1Si3 (391.11): calcd C 46.07, H 8.25, N 7.16; found C 46.47, H 8.66, N 7.36. Synthesis of N,N′,N′-[Tris(trimethylsilyl)]hydrazino-(dichloro)phosphane, (TMS)2N-(TMS)N-PCl2 (3). 3 was prepared according to the procedure given in the literature.16 3 can be purified further by sublimation (65 °C, 10-3 mbar). (TMS)2N-(TMS)NPCl2 (349.46) yield: 90% colorless ceraceous crystals, mp 114 °C (slow dec). Raman (200mW, 25 °C, cm-1): ν˜ 2960 (5), 2904 (10), 1411 (2), 687 (2), 658 (2), 645 (7), 585 (1.5), 466 (4), 448 (4), 438 (4), 364 (4), 351 (4), 232 (4, br), 188 (4, br), 144 (2, br). 1H NMR (CDCl3, 25 °C): δ 0.19 (s, 18 H, TMS), 0.38 (s, 9 H, TMS). 13C NMR (CDCl3, 25 °C): δ 2.46 (s, NSi(CH3)3)2), 2.51 (s, NSi(CH3)3). 31P NMR (CDCl , 25 °C): δ 166.6 (s). 29Si{1H} NMR (CDCl , 25 3 3
Phosphorus Attached to a N-N Unit Table 1. Crystallographic Data
formula fw cryst syst space group a, Å b, Å c, Å R, deg β, deg γ, deg V, Å3 Z Fcalcd, g/cm-3 µ, mm-1 λMo KR, Å T, K reflns collected independent reflns Rint obsd reflns F(000) R1a wR2b GOF No. parameters CCDC no. a
1
2
4
8
C21H37N2PSi3 432.77 triclinic P1h 9.0109(7) 9.3520(8) 15.344(1) 84.454(1) 85.441(2) 81.534(2) 1270.2(2) 2 1.132 0.259 0.71073 193 5442 2807 0.019 2451 468 0.0375 0.1024 1.044 253 242754
C15H32ClN2PSi3 391.11 monoclinic P21/n 15.581(1) 9.2489(8) 16.215(1) 90 110.908(8) 90 2182.8(3) 4 1.190 0.412 0.71073 200 10197 2838 0.094 1573 840 0.0394 0.0802 0.78 199 242755
C21H37N2PSSi3 464.83 monoclinic P21/n 8.8653(1) 37.6480(4) 16.0046(2) 90 93.2525(4) 90 5333.1(1) 8 1.158 0.326 0.71073 200 43715 7350 0.081 4734 2000 0.0476 0.1198 1.04 505 242756
C34Cl2H86Mg3N4O8P2Si6 1053.35 monoclinic P21/n 13.669(3) 27.625(6) 15.347(3) 90 98.47(3) 90 5732(2) 4 1.221 0.371 0.71073 200 83838 13116 0.097 9196 2264 0.0509 0.1408 1.04 532 242757
Final R [F > 2σ(F)]. b R indices (all data).
°C): δ 13.7 (d, 3JSiP ) 2.0 Hz, N(Si(CH3)3)2), 19.8 (d, 2JSiP ) 6.9 Hz, NSi(CH3)2). For MS and CHN analytical data, see ref 16. Synthesis of MgCl2(THF)2‚2 Mg[N(TMS)P(O)2N(TMS)2](THF) (8). Into a solution of 1.747 g (5.00 mmol) of 3 in 100 mL THF, 0.486 g (20.0 mmol) of magnesium splinters was added at 0 °C. The reaction mixture was allowed to warm to ambient temperature after 3 h at 0 °C and was stirred for 70 h. The solution was filtered, and the solvent was removed in vacuum. The remaining orange oil was recrystallized from anhydrous hexane over a period of 14 days. We assume that oxygen was introduced by either THF or during the recrystallization procedure.17 When we attempted to isolate a sample for elemental analysis, the crystals released solvent molecules, hence the reported data are fairly inaccurate. MgCl2(THF)2‚2Mg[N(TMS)P(O)2N(TMS)2](THF) (1053.38) yield: ca. 8% colorless blocks, mp none (upon heating, THF liberation). Raman (200 mW, 25 °C, cm-1): ν˜ 2960 (8), 2900 (10), 1451 (2, br), 1409 (2, br), 1250(2, br), 1038 (2), 923 (2), 892 (1), 880 (1), 670 (3), 629 (4), 437 (3), 242 (3), 224 (3.5). 1H NMR (CDCl3, 25 °C): δ 0.48 (s, 3 H, Si(CH3)3), 1.34 (s, 1 H, THFcoord.), 3.91 (s, 1H, THFcoord.). 13C NMR (CDCl3, 25 °C): δ 6.1 (s, Si(CH3)3), 24.9 (THFcoord.), 69.7 (THFcoord.). 31P NMR (CDCl3, 25 °C): δ 9.5 (s, br, (TMS)2NP(O)2N(TMS)2-). 29Si{1H} NMR (CDCl3, 25 °C):δ -7.1 (s). MS (FAB-, xenon, 6keV, m-NBA matrix): 311 [Manion + H+]-, 239 [Manion + 2H+ - TMS+]-. C34Cl2H86Mg3N4O8P2Si6 (1053.38): calcd C 38.77, H 8.23, N 5.32; found C 25.51, H 6.25, N 6.32. X-ray Analyses. X-ray quality crystals of 1, 2, and 4 were obtained by sublimation (see Experimental Section). X-ray quality crystals of 8 were obtained from a yellow hexane/THF solution of 8 after the stepwise removal of solvent. Data for compound 1 were collected on a Siemens CCD area detector using Mo KR radiation (CCDC 242754), data for 2 were collected on a STOE IPDS (CCDC 242755), and the data for 4 (CCDC 242756) and 8 (CCDC 242757) (17) Kessenich, E.; Polborn, K.; Schulz, A. Z. Anorg. Allg. Chem. 2001, 627, 2506-2510.
were collected on a Nonius Kappa CCD, Mo KR. Crytallographic data are summarized in Table 1. Selected bond lengths and angles are available in Tables S1-S4 (Supporting Information). All of the structures were solved by direct methods (the structure solution program for 1 was SHELXS-97, and SIR9718 was used for 2-4) and refined by full-matrix least-squares methods with SHELXL97.19 Hydrogen atoms were included at geometrically idealized positions and were not refined; the non-hydrogen atoms were refined anisotropically. Computational Details. Our goal was to compare the structures and energetics of different NNP species attached to 3-1 trimethylsilyl groups. Therefore, it was important to carry out the calculations in such a way that the results could be compared reliably with each other. The structural and vibrational data of all of the considered species were calculated by using hybrid density functional theory (B3LYP) with the program package Gaussian 98.20 We ran two sets of computations: (i) for all elements, a standard 6-31G(d,p) basis set was used, and (ii) a 6-311+G(3df,2p) standard basis set was applied only for those species with only one TMS group. Comparison of these data sets shows differences in bond lengths no larger than 0.01-0.02 Å. The bond angles in all of these (18) Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, G. L.; Giacorazzo, C. J. Appl. Crystallogr. 1999, 32, 115-119. (19) Sheldrick, G. M. SHELXL-97: Program for Solution of Crystal Structures; University of Go¨ttingen: Go¨ttingen, Germany, 1997. (20) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Zakrzewski, V. G.; Montgomery, J. A., Jr.; Stratmann, R. E.; Burant, J. C.; Dapprich, S.; Millam, J. M.; Daniels, A. D.; Kudin, K. N.; Strain, M. C.; Farkas, O.; Tomasi, J.; Barone, V.; Cossi, M.; Cammi, R.; Mennucci, B.; Pomelli, C.; Adamo, C.; Clifford, S.; Ochterski, J.; Petersson, G. A.; Ayala, P. Y.; Cui, Q.; Morokuma, K.; Malick, D. K.; Rabuck, A. D.; Raghavachari, K.; Foresman, J. B.; Cioslowski, J.; Ortiz, J. V.; Stefanov, B. B.; Liu, G.; Liashenko, A.; Piskorz, P.; Komaromi, I.; Gomperts, R.; Martin, R. L.; Fox, D. J.; Keith, T.; Al-Laham, M. A.; Peng, C. Y.; Nanayakkara, A.; Gonzalez, C.; Challacombe, M.; Gill, P. M. W.; Johnson, B. G.; Chen, W.; Wong, M. W.; Andres, J. L.; Head-Gordon, M.; Replogle, E. S.; Pople, J. A. Gaussian 98, revisions A7 and A11; Gaussian, Inc.: Pittsburgh, PA, 1998.
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Fischer et al. molecules are rather constant and relatively independent of the basis sets. Finally, to save CPU time and to obtain a consistent set of data, we decided to use a 6-31G(d,p) basis for all of the molecules.21 All of the stationary points were characterized by frequency analysis at the B3LYP level. To obtain more reliable energies and to check the quality of the smaller 6-31G(d,p) basis set, we calculated single points for all of the species by using the optimized B3LYP/6-31G(d,p) structure and the larger 6-311+G(3df,2p) basis set, notation B3LYP/6-311+G(3df,2p))//B3LYP/6-31G(d). The mean deviation for the energies utilizing both basis sets is reasonably small at 2.7 kcal/mol. NBO analyses22 were carried out to investigate the bonding in all of the molecules at the SCF level by utilizing the optimized B3LYP/6-31G(d,p) geometry. Furthermore, NBO population analysis for 1 and 2 was carried out with the structure fixed at that determined by X-ray analysis of 1 and 2 to investigate the bonding and hybridization in this experimentally observed species (single point at the HF level). The search for transition states was usually started with scans along an estimated reaction coordinate. Once a transition state was located, we carried out intrinsic reaction coordinate (IRC) calculations to check whether the located transition states belong to either of the two minima under consideration. Two hundred points in both directions were calculated. In cases in which 200 steps did not lead to a minimum, an optimization followed that utilized the last geometry of the IRC. Because of the existence of several methyl groups in all of the species, we also had to study the conformational space. In case we were able to find rotamers that are very close in energy, we have calculated the weight factors according to the Boltzmann approach. The computed geometrical parameters for all of the molecules are given as Supporting Information in Tables S5 and S6, and the relative energies are given in Table 2. Details of the NBO analyses are summarized in Table 3. The computed frequencies and absolute energies are given in the Supporting Information; the IRCs can be obtained from the authors. Molecular models and the numbering of atoms are shown in Figures 1, 6, and 9-12. In our discussion, unless otherwise noted, B3LYP/6-31G(d,p) geometries and energies will be quoted. It should be emphasized that the computation was carried out for a single, isolated (gas-phase) molecule. There may be significant differences among gas-phase, solution, and solid-state data.
Results and Discussion Reaction of Ph2PCl, PhPCl2, and PCl3 with [LiN(TMS)N(TMS)2]2. The salt-elimination reaction of di(chloro)phenylphosphane chloride with bis[lithium-tris(trimethylsilyl)-hydrazide] in hexane at ambient temperature represents a fast and clean reaction (reaction time 1 h, yield > 90%), resulting in the formation of hydrazino(diphenyl)phosphane 1, (TMS)2N-(TMS)N-PPh2, (eq 3, n ) 2, TMS (21) Klapo¨tke, T. M.; Schulz, A. Ab Initio Methods in Main Group Chemistry (with an invited chapter by R. D. Harcourt about VB Theory); John Wiley & Sons: New York, 1998. (22) (a) Glendening, E. D.; Reed, A. E.; Carpenter, J. E.; Weinhold, F. NBO, version 3.1; (b) Carpenter, J. E.; Weinhold, F. J. Mol. Struct: THEOCHEM 1988, 169, 41. (c) Foster, J. P.; Weinhold, F. J. Am. Chem. Soc. 1980, 102, 7211. (d) Reed, A. E.; Weinhold, F. J. Chem. Phys. 1983, 78, 4066. (e) Reed, A. E.; Weinstock, R. B.; Weinhold, F. J. Chem. Phys. 1985, 83, 735. (f) Reed, A. E.; Schleyer, P. v. R. J. Am. Chem. Soc. 1987, 109, 7362. (g) Reed, A. E.; Schleyer, P. v. R. Inorg. Chem. 1988, 27, 3969. (h) Weinhold, F.; Carpenter, J. E. The Structure of Small Molecules and Ions; Plenum Press: New York, 1988; p 227.
1744 Inorganic Chemistry, Vol. 44, No. 6, 2005
Table 2. Relative Energies (kcal/mol) of All Considered Species Fully Optimized at B3LYP/6-31G(d)a species
∆E
∆E(LB)b
∆H298
∆G298
3a 3b 3_1r 3_2a + TMS-Cl 3_2b + TMS-Cl 3_2c + TMS-Cl 3_2d + TMS-Clc 3_2e + TMS-Clc 3_2r + TMS-Cl 3_2r2 + TMS-Cl 3_3a + 2TMS-Cl 3_3b + 2TMS-Cl 3_3c + 2TMS-Cl 3_3r + 2TMS-Cl TS1 TS2a TS2b TS3 + TMS-Cl TS4 + TMS-Cl TS5 + TMS-Cl TS6 + TMS-Cl TS7 + TMS-Cl TS8 + TMS-Cl TS9 TS10 TS11 + TMS-Cl TS12 + 2TMS-Cl TS13 + 2TMS-Cl TS14 + 2TMS-Cl TS15 + TMS-Cl TS16 + TMS-Cl
0.0 2.3 34.6 -5.3 16.9 20.3 -16.8 -16.4 7.4 14.7 -1.9 27.1 -3.6 41.1 10.0 47.0 42.4 27.9 33.3 22.7 42.2 49.0 35.0 34.6 47.9 57.0 63.0 63.2 50.3 42.1 42.8
0.0 2.33 35.68 -3.01 19.84 23.72 -27.2 -27.3 5.13 11.7 1.75 20.13 1.47 43.70 9.94 47.46 44.67 30.50 34.47 24.92 48.26 53.02 38.89 35.76 48.68 54.71 66.66 59.46 53.84 37.9 34.3
0.0 2.5 34.3 -6.5 15.4 18.8 -17.8 -17.5 5.5 12.9 -4.2 24.3 -6.2 37.4 9.4 39.4 41.6 25.4 30.6 20.3 40.0 46.4 33.0 33.7 47.1 53.9 58.6 58.5 46.8 39.1 40.5
0.0 4.0 33.5 -20.6 0.7 3.7 -34.4 -34.6 -8.7 -1.7 -31.4 -3.8 -33.5 10.2 12.1 45.4 42.8 10.6 16.4 6.8 25.7 32.4 19.8 35.5 48.4 40.1 31.5 31.4 21.2 23.3 24.9
1_an 2_an TS_an
0.0 -56.7 2.6
0.0 -63.8 1.3
0.0 -56.1 1.5
0.0 -57.3 1.9
a ∆E relative (to 3a or 1_an) energy at 0 K without zpe correction. b LB ) large basis set: B3LYP/6-311+G(3df,2p)//B3LYP/6-31G(d,p). c Conformational averaging gives ∆E ) -16.5, ∆E(LB) ) -27.3, and ∆G298 ) -34.4 kcal/mol.
Table 3. Summary of the NBO Analysis of 1, 2, and 3 (Net Charges in e, LP(X) f σ*(YZ) Donor-Acceptor Interactions in kcal/mol)a-c 1 QP QN1 QN2 QL1a QL2a
+1.093 -1.043 -1.179 -0.372 -0.388
2 +1.221 -1.119 -1.204 -0.458 -0.412
3a 1.208 -1.157 -1.244 -0.397 -0.368
spλ LP(P), λ ) 1.19 0.73 0.45 σ(PN): c(P)2/c(N)2 in % 25.7/74.3 22.7/77.3 23.5/76.5 LP(N1) f σ*(PL1) 7 2 23 LP(N1) f σ*(PL2) 6 24 7 LP(P1) f σ*(N1N2) 10
